1. Field of the Invention
This invention relates to an ink jet recording head discharging ink from an ink discharging opening based on recording information, and an ink jet recording device having said ink jet recording head, as well as a method for operating said ink jet recording head.
2. Related Background Art
An ink jet recording device supplies ink to a recording head and discharges ink through an ink discharging opening provided at said recording head based on recording information, thereby effecting recording using ink droplets flying from the ink discharging opening toward an recording medium such as a recording sheet.
As an example of the ink jet recording head, there has been used structure in which a plurality of ink discharging openings communicate with one common liquid chamber. FIG. 4 depicts schematically such an example of the ink jet recording head of the prior art.
In FIG. 4, on an ink discharging surface (at the front end of the recording head 1 in this drawing) are formed a plurality of ink discharging openings 2 according to a predetermined arrangement, and liquid pathways 3 extended from the respective ink discharging openings communicate with a liquid chamber 4 formed internally of the head 1. In FIG. 4, however, only some of the liquid pathways arranged at or near the ends of opening array are shown. Ink from the ink feeding source (for example, an ink tank of cartridge type that is not shown) is fed through a feeding pipe 5 to the liquid chamber 4. In the example shown in FIG. 4, the feeding pipe 5 is connected through a L-joint to the liquid chamber forming member 4.
The recording head described above has its respeotive constituting members assembled on a base plate 7.
FIGS. 5(A), 5(B) and 5(C) are schematic sectional drawings for showing the mechanism of ink discharging in the head 1.
In FIG. 5(A), ink 10 fed through the feeding pipe 5 is filled in the liquid chamber 4 and the respective liquid pathways 3, and on the wall surfaces of the respective liquid pathways 3 are provided heaters 11 as means for generating energy utilized to discharge ink 10. When signals are applied from a driving system not shown on the heaters 11 of the respective liquid pathways 3, an abrupt pressure change preferably accompanied by bubble formation causes ink 10 to discharge from the ink discharging openings 2.
The numeral 13 shows the meniscus of ink at the discharging opening 2.
In this case, the pressure wave 14 generated is propagated not only in the direction toward the ink discharging opening 2 but also in the direction toward the common liquid chamber as indicated in FIG. 5(B).
Particularly, when ink is discharged simultaneously from a number of liquid pathways 3, the pressure wave 14 sometimes cannot be disregarded. More specifically, when a pressure wave denoted by the numeral 14 is generated as in FIG. 5(B), ink 10 not only in the liquid chamber 4 but also in the feeding pipe 5 is affected thereby, whereby the force in the direction opposite to the ink feeding direction will act on the ink 10. As a result, feeding of ink is obstructed to slow the refilling (supplementing) speed of ink 10.
As a consequence, a next pulse signal is applied to the heater 11 under an after incomplete refilling to initiate next ink discharging, whereby there sometimes ensues a problem such that poor ink discharging occurs such reduced ink dot diameter or retarded ink discharging speed.
Such a problem is liable to occur particularly in the ink jet recording head of high speed printing type or large ink dot discharging type, and it has been an obstacle in acceleration of printing speed or formation of multi-nozzle head.
To solve this problem by absorbing the pressure change in a liquid chamber, air space may be provided in the liquid chamber as described in, for example, U.S. Pat. No. 4,158,874. In this constitution, however, a larger height of liquid chamber shall be required, thus resulting in enlargement of the recording head. Further, since the height of the liquid chamber becomes greater than the height of the discharging opening bearing portion, there is brought about a problem such that a user can not see printed letters immediately after ink discharging.
On the other hand, in FIG. 2 of U.S. Pat. No. 4,596,994, it is disclosed that another liquid chamber 206 is provided as communicating with a common liquid chamber 205. However, in this patent document, the liquid chamber 206 is not disclosed as containing space formed therein, and is not necessarily considered to have a pressure wave absorbing function (damper effect) since the liquid chamber 206 is provided at the side having an energy generating means.